Support Control Patterns in a UI Automation Provider

This topic shows how to implement one or more control patterns on a UI Automation provider so that client applications can manipulate controls and get data from them.

Support Control Patterns

1. Implement the appropriate interfaces for the control patterns that the element should support, such as IInvokeProvider for InvokePattern.

2. Return the object containing your implementation of each control interface in your implementation of System.Windows.Automation.Provider.IRawElementProviderSimple.GetPatternProvider(System.Int32)

Example

The following example shows an implementation of ISelectionProvider for a single-selection custom list box. It returns three properties and gets the currently selected item.

#region ISelectionProvider Members

/// <summary>
/// Specifies whether selection of more than one item at a time is supported.
/// </summary>
public bool CanSelectMultiple
{
    get
    {
        return false;
    }
}

/// <summary>
/// Specifies whether the list has to have an item selected at all times.
/// </summary>
public bool IsSelectionRequired
{
    get
    {
        return true;
    }
}

/// <summary>
/// Returns the automation provider for the selected list item.
/// </summary>
/// <returns>The selected item.</returns>
/// <remarks>
/// MyList is an ArrayList collection of providers for items in the list box.
/// SelectedIndex is the index of the selected item.
/// </remarks>
public IRawElementProviderSimple[] GetSelection()
{
    if (SelectedIndex >= 0)
    {
        IRawElementProviderSimple itemProvider = (IRawElementProviderSimple)MyList[SelectedIndex];
        IRawElementProviderSimple[] providers =  { itemProvider };
        return providers;
    }
    else return null;
}
#endregion ISelectionProvider Members

#Region "ISelectionProvider Members"

''' <summary>
''' Specifies whether selection of more than one item at a time is supported.
''' </summary>

Public ReadOnly Property CanSelectMultiple() As Boolean _
    Implements ISelectionProvider.CanSelectMultiple
    Get
        Return False
    End Get
End Property
''' <summary>
''' Specifies whether the list has to have an item selected at all times.
''' </summary>

Public ReadOnly Property IsSelectionRequired() As Boolean _
    Implements ISelectionProvider.IsSelectionRequired
    Get
        Return True
    End Get
End Property

''' <summary>
''' Returns the automation provider for the selected list item.
''' </summary>
''' <returns>The selected item.</returns>
''' <remarks>
''' MyList is an ArrayList collection of providers for items in the list box.
''' SelectedIndex is the index of the selected item.
''' </remarks>
Public Function GetSelection() As IRawElementProviderSimple() _
    Implements ISelectionProvider.GetSelection
    If SelectedIndex >= 0 Then
        Dim itemProvider As IRawElementProviderSimple = DirectCast(MyList(SelectedIndex), IRawElementProviderSimple)
        Dim providers(1) As IRawElementProviderSimple
        providers(0) = itemProvider
        Return providers
    Else
        Return Nothing
    End If

#End Region
Private Members As ISelectionProvider

The following example shows an implementation of GetPatternProvider that returns the class implementing ISelectionProvider. Most list box controls would support other patterns as well, but in this example a null reference (Nothing in Microsoft Visual Basic .NET) is returned for all other pattern identifiers.

/// <summary>
/// Returns the object that supports the specified pattern.
/// </summary>
/// <param name="patternId">ID of the pattern.</param>
/// <returns>Object that implements IInvokeProvider.</returns>
/// <remarks>
/// In this case, the ISelectionProvider interface is implemented in another provider-defined class, 
/// ListPattern. However, it could be implemented in the base provider class, in which case the 
/// method would simply return "this".
/// </remarks>
object IRawElementProviderSimple.GetPatternProvider(int patternId)
{
    if (patternId == SelectionPatternIdentifiers.Pattern.Id)
    {
        return new ListPattern(myItems, SelectedIndex);
    }
    else
    {
        return null;
    }
}

''' <summary>
''' Returns the object that supports the specified pattern.
''' </summary>
''' <param name="patternId">ID of the pattern.</param>
''' <returns>Object that implements IInvokeProvider.</returns>
''' <remarks>
''' In this case, the ISelectionProvider interface is implemented in another provider-defined class, 
''' ListPattern. However, it could be implemented in the base provider class, in which case the 
''' method would simply return "this".
''' </remarks>
Function GetPatternProvider(ByVal patternId As Integer) As Object _
    Implements IRawElementProviderSimple.GetPatternProvider

    If patternId = SelectionPatternIdentifiers.Pattern.Id Then
        Return New ListPattern(myItems, SelectedIndex)
    Else
        Return Nothing
    End If

End Function 'IRawElementProviderSimple.GetPatternProvider

See Also

Concepts

UI Automation Providers Overview
Server-Side UI Automation Provider Implementation